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UNITED STATES PATENT OFFICE.

WALTER J .'-KOI-ILER, OF SHEBOYGAN, AND ANTON BROTZ, OF KOI-ILER, WISCONSIN,

ASSIGNORS' TO KOI-ILER 60., OF KOI-ILER, WISCONSIN, A CORPORATION OF WIS- consm.

METAL MOLDING.

Specification of Letters Patent.

Patented Dec. 23, 1919.

N0 Drawing. Continuation of application Serial No. 253,275, filed September 9, 1918. This application filed January 22, 1919. Serial No. 272,566.

To all-whom it may concern:

Be it known that we, \VALTER J. KOHLER and ANTON Bno'rz, citizens of the United States, and residents of Sheboygan and Kohler, respecti ely Sheboygan county, Visconsin, have invented new and useful Improvements in Metal Molding, of which the following is a description, reference' steel or semi-steel in metal molds, known as permanent molds, without producing the usual chill or hardening of the casting. and, consequently, produclng a casting 1n condition for machining or enameling.

It has heretofore been proposed, in order to obtain economical, quantity production in the n'ianufacture of ordnance shells, to use permanent molds, notwithstandlng the tendency, ordinarily. of the semi-steel casting to chill from the rapid conduction of heat therefrom by the mold. This proposal contemplated the employment of an annealing process to remove .the chill and render the shell capable of being machined.

The object of the present invention is to render unnecessary such annealing process with its unreliability, delay in production. and increased cost.

Primarily,- the invention consists in ap-' plying to the surface'of the mold cavity a coating which, by reason of its being partly absorbed by the molten metal. or by reason of its non-conducting properties,- or both. prevents the casting from being chilled by the mold.

As at present preferred. the invention in practice makes use of a mold coating containing commercially pure silica and an ingredient to cause this silica to be held in suspension in water so that it can be used as a spray or a wash. The silica may con sist of quartz, flint. silica sand, or the like.

The ingredient to cause the silica to be held in suspension 111 water may consist of clay. The silica and the clay are preferably ground together in water to a definite de gree of fineness. This mixture of the confrom pitting or. imperfections.

In practice it is preferred in the begin-- ning of operations to first heat the metal mold to a temperature of about 300 degrees Fahrenheit and then apply the liquid coat-' ing evenly over the 'entire surface of the mold cavity by means of an atomizer. The

liquid quickly dries, leaving the spray'ingredients adhering to the metal mold walls. The metal is poured in the usual manner and after allowing a few minutes to set,

depending upon the nature of the casting and the composition of the metal used, the

mold is opened and the casting is removed.

The coatlng can then be 'brushed off of the mold and a new coating sprayed on it for the next operation without reheating.

The casting may be allowed to cool in the open or slowly cool.

hen cold, the casting will be found to be free from chill and uniformly soft throughout and can bemachined or enameled without annealing. It is superior. to a casting made of chilling metal cast in a sand mold. 'The latter may chill at certain points, while castings of the same metal made by this process do not chill. Not only is the chill' prevented by this process, but

placed in a, pit where it will the metal of the casting appears to be'supesile strength and hydraulic tests required for ordnance projectiles equally as wclhas those cast in the sand mold, and are freer The metal is close grained, readily'machined or enameled, of great strength and ductile.

It is believed that the avoidance of chill and the-superior qualitiesof the castings are due to an absorption of the silica. tlienon-conductivity of the coating and the purity, of the materials used.

the surface only.

The addition of silica to the molten composition does not produce the same result. but causes a weakening of the metal so that it will not comply with the impact and tensile strength tests required for semi-steel The effect is. uniform throughout the. casting and not at ordnance" shell. The mold coating also serves as a protection for the mold. and aids in the removal of the casting.

When the casting is removed the mold is immediately available for the next operationand may be used indefinitel as thousands of castings can be poured in one mold before it is affected and unsuitable for fur-.

ther use.

As compared with all methods of sand molding, and particularly in the manufacture of semi-steel shells, in which it lSLllGC- essary to ordinarily leave the casting in the sand mold for about four or five hours.

.there is a great saving in labor, material and and enameling operations, which, because of the superior-quality of the casting, can be more efliciently, economically and uniformly performed. 7

The effect of the process on the metal castin improves it for galvanizing, tinning, ename ing, or similar coating operations.

\Vhen it is desired that the casting should be chilled at one part and soft at another,

'the m-oldmay be treated locally with this coating.

.Of the silica containing ingredients, com- 1nercial1y pure quartz, used in enameling operations, is found to be very suitable for the purpose, and it is preferred to use enamelers clay in order to keep the quartz in suspension.

Very satisfactory results have been obtained with semi-steel castings, after first heating the mold to a temperature of about 300 degrees, by spraying themold with a composition composed of pulverized quartz,

,'90 parts by weight; white clay, 10' parts;

and water. The purity of the ingredients, the thorough mixing of the. composition and the degree of fineness of the grinding contributes largely to the success of the process.

'Ihe casting may be made in a permanent metal mold with a permanent metal core.

if it can be withdrawn. both mold and core being coated with the composition to prevent the chill.

Wh1le We have stated preferred ingre dients and methods of application of the mold coating, we do not wish to confine ourselves thereto, as it is obvious that others may be substituted without departing from the invention as herein claimed.

The process as described can be carried out in large operations without in any way injuriously affecting the health and comfort of the workman.

It is understood that we do not confine ourselves to this process for the manufacture of semi-steel shells, for it is adapted for castings of any metal of any nature which can be successfully made in sand molds.

What we claim as new and desire to secure by Letters Patent is:

1. The method of casting metal in permanent metal molds without producing chill, which consists in coating or spraying a moderately heated metal mold with a coating containing pulverized, commerci ally pure silica and then pouring the metal into the mold.

2. The method of avoiding chill in permanent metal mold castings. which consists in spraying the metal mold with a spray consisting of commercially pure silica and con'imercially pure clay.

3. The method of producing soft. castings of easy chilling metal in permanent metal molds, which consists incoating the mold with a composition consisting of pulverized silica and clay.

l. The method of preventing chill in permanent metal mold castings, which consists in coating the mold with ground quartz and white clay.

5. The method of preventing chill in permanent metal mold castings, which consists in coating the mold with a composition of ground quartz, substantially 90 parts by weight, and white clay, substantially 10 parts, ground in Water.

6. A permanent metal mold, for use in making metal castings, having its face coated with a coveringof commercially pure silica. I

7. A coating for permanent metal molds, to avoid chill in metal castings, consisting of pulveried commercially pure silica, clay and Water.

8. A mold coating for preventing chill in permanent metal mold castings, which consists of ground quartz substantially 90 parts by weight,'and white clay substantially 10 parts, ground in water.

In testimony whereof we afiix our signatures, in presence of two witnesses.

WALTER J. KOHLER. ANTON BROTZ.

Witnesses.

O. A. Knoos, B. M. HEITZER. 

